Room temperature curable organopolysiloxane compositions

Details Room temperature curable organopolysiloxane compositions Room temperature curable organopolysiloxane compositions

2003-06-30

2004-10-26

Moore, Margaret G. (Department: 1712)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

At least one aryl ring which is part of a fused or bridged...

C524S268000, C525S477000, C528S017000, C528S034000

Reexamination Certificate

active

06809136

ABSTRACT:

This invention relates to room temperature curable organopolysiloxane compositions, and more particularly, to room temperature curable organopolysiloxane compositions which are adherent to difficult-to-bond resins used as sealants or for bonding and securing of electric and electronic parts.
BACKGROUND OF THE INVENTION
Various types of room temperature curable organopolysiloxane compositions are well known in the art which cure into elastomers at room temperature upon contact with air-borne moisture. Among others, those compositions of the type that cure while releasing alcohol are preferentially used in sealing, bonding and coating of electric and electronic equipment, owing to their advantageous features of no disgusting odor and no corrosion of metals. One typical composition of this type is described in JP-B 39-27643 as comprising an organopolysiloxane end-blocked with hydroxyl groups, an alkoxysilane, and an organic titanium compound. Also JP-A 55-43119 discloses a composition comprising an organopolysiloxane end-blocked with alkoxysilyl groups, an alkoxysilane, and alkoxy titanium. JP-B 7-39547 discloses a composition comprising an organopolysiloxane end-blocked with alkoxysilyl groups (including silethylene), an alkoxysilane, and alkoxy titanium. JP-A 62-207369 discloses a composition comprising an alkoxysilyl end-capped organopolysiloxane, a hydroxyl-terminated organopolysiloxane, an alkoxysilane and titanium. Allegedly improvements are made in resistance to oil swelling and shelf life. For these compositions of the type that cure while releasing alcohol, engineers have made efforts to improve the preparation method, shelf stability (suppression of changes with time) and various properties, typically resistance to oil swelling. Although the above-referred compositions appear analogous, the individually specified composition has an important meaning in positively acquiring the desired set of properties.
Meanwhile, with the sophistication of techniques of improving the durability of resins, many of the resins currently used in housings of electric and electronic appliances are not bondable with conventional sealants. The above-referred compositions used for sealing, bonding and coating in electric and electronic equipment are not fully adherent to these resins.
SUMMARY OF THE INVENTION
An object of the invention is to provide a room temperature curable organopolysiloxane composition which is fully adherent to difficult-to-bond resins used as sealants or for bonding and securing of electric and electronic parts. We have found that by using an organopolysiloxane having at least two organooxysilyl groups in a molecule as a base polymer, and adding thereto specific amounts of a hydroxyl end-capped organopolysiloxane, an organooxysilane or partial hydrolytic condensate thereof, and a titanium chelate catalyst, there is obtained an organopolysiloxane composition which has shelf stability and is dramatically improved in adhesion to those resins which are believed to be difficult to bond. The present invention is predicated on this finding.
Accordingly, the present invention provides a room temperature curable organopolysiloxane composition comprising components (A) to (D):
(A) 100 parts by weight of an organopolysiloxane having at least two organooxysilyl groups in a molecule, represented by the following general formula (1) or average formula (2) or (3):
wherein R
1
is a monovalent hydrocarbon group, R
2
is a monovalent hydrocarbon group or alkoxy-substituted monovalent hydrocarbon group, R
3
is a substituted or unsubstituted monovalent hydrocarbon group, Y is an oxygen atom or divalent hydrocarbon group having 1 to 8 carbon atoms, b is an integer of 1 to 3, c, d, e and m each are an integer of at least l, k is an integer of at least 2, and c, d+m and e+k in the formulae are each such an integer that the organopolysiloxane has a viscosity of 20 to 1,000,000 centipoises at 25° C.,
(B) 1 to 30 parts by weight of a hydroxyl-terminated linear organopolysiloxane having the following general formula (4):
wherein R
3
is substituted or unsubstituted monovalent hydrocarbon group and f is such an integer that the organopolysiloxane has a viscosity of 20 to 1,000,000 centipoises at 25° C.,
(C) 0.5 to 15 parts by weight of an organooxysilane having the general formula: R
1
a
Si(OR
2
)
4-a
wherein R
1
is a monovalent hydrocarbon group, R
2
is a monovalent hydrocarbon group or alkoxy-substituted monovalent hydrocarbon group, and “a” is 0 or 1, or a partial hydrolytic condensate thereof, and
(D) 0.1 to 10 parts by weight of a titanium chelate catalyst.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The room temperature curable organopolysiloxane composition is arrived at by using as a base polymer an organopolysiloxane having per molecule at least two silicon atoms each attached to an organooxy group through an oxygen atom or divalent hydrocarbon group and compounding therewith specific amounts of a hydroxyl end-capped organopolysiloxane, an organooxysilane or partial hydrolytic condensate thereof, and a titanium chelate compound as a catalyst.
Component (A), which serves as a base polymer of the inventive composition, is an organopolysiloxane having per molecule at least two, preferably 2 to 10 silicon atoms each attached to an organooxy group, especially alkoxy group through an oxygen atom or divalent hydrocarbon group. Namely, component (A) is one or more organooxysilyl group-containing organopolysiloxanes having the following general formula (1), average formula (2) and average formula (3). It is noted that the average formula means that siloxane units having pendant alkoxy groups may be discretely dispersed rather than being blocked together.
Herein R
1
is a monovalent hydrocarbon group, R
2
is a monovalent hydrocarbon group or an alkoxy-substituted monovalent hydrocarbon group, R
3
is a substituted or unsubstituted monovalent hydrocarbon group, Y is an oxygen atom or divalent hydrocarbon group having 1 to 8 carbon atoms, b is an integer of 1 to 3, c, d, e and m each are an integer of at least l, k is an integer of at least 2, and c, d+m and e+k in the formulae are each such an integer that the organopolysiloxane has a viscosity of 20 to 1,000,000 centipoises at 25° C.
In the organopolysiloxanes of the general formula (1) or the average formula (2) or (3), the monovalent hydrocarbon groups represented by R
1
and R
3
are preferably unsubstituted or substituted (halogen, cyano or otherwise substituted) monovalent hydrocarbon groups having 1 to 12 carbon atoms, especially 1 to 10 carbon atoms, for example, alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, and octadecyl, cycloalkyl groups such as cyclopentyl and cyclohexyl, alkenyl groups such as vinyl and allyl, aryl groups such as phenyl, tolyl and naphthyl, and aralkyl groups such as benzyl, phenylethyl and phenylpropyl. Exemplary of halogenated hydrocarbon groups are chloromethyl, trifluoromethyl, chloropropyl, 3,3,3-trifluoropropyl, chlorophenyl, dibromophenyl, tetrachlorophenyl, and difluorophenyl. Exemplary of cyanoalkyl groups are &bgr;-cyanoethyl, &ggr;-cyanopropyl and &bgr;-cyanopropyl. Of these, methyl is most preferred.
For R
2
, hydrocarbon groups of 1 to 10 carbon atoms, especially 1 to 4 carbon atoms are preferred. Examples of suitable monovalent hydrocarbon groups are as described above. Typical examples include alkyl groups such as methyl, ethyl, propyl, butyl, hexyl and octyl, and alkoxy-substituted alkyl groups such as methoxyethyl, ethoxyethyl, methoxypropyl and methoxybutyl. Of these, methyl and ethyl are most preferred.
Desirably, each of R
1
, R
2
and R
3
has 1 to 3 carbon atoms, and is most desirably methyl.
Y is an oxygen atom or a divalent hydrocarbon group. Suitable divalent hydrocarbon groups are alkylene groups having 1 to 8 carbon atoms, especially 1 to 6 carbon atoms, such as —CH
2
CH
2
—, —CH
2
CH
2
CH
2
— and —CH
2
C(CH
3
)H—, with —CH
2
CH
2
—being most preferred.
The subscripts b, m and k are as defined above, b is preferably 2 or 3, m is preferably 1 to

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